Dry etch process

ABSTRACT

A method for conformal dry etch of a liner material in a high aspect ratio trench is achieved by depositing or forming an inhomogeneous passivation layer which is thicker near the opening of a trench but thinner deep within the trench. The method described herein use a selective etch following formation of the inhomogeneous passivation layer. The selective etch etches liner material faster than the passivation material. The inhomogeneous passivation layer suppresses the etch rate of the selective etch near the top of the trench (where it would otherwise be fastest) and gives the etch a head start deeper in the trench (where is would otherwise be slowest). This method may also find utility in removing bulk material uniformly from within a trench.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/724,767 by Zhang et al, filed Nov. 9, 2012, and titled “DRY ETCHPROCESS.” This application also claims the benefit of U.S. ProvisionalApplication No. 61/732,074 by Kim et al, filed Nov. 30, 2012 and titled“DRY-ETCH FOR SELECTIVE OXIDATION REMOVAL.” Each of the above U.S.Provisional Applications is incorporated herein in its entirety for allpurposes.

BACKGROUND OF THE INVENTION

Integrated circuits are made possible by processes which produceintricately patterned material layers on substrate surfaces. Producingpatterned material on a substrate requires controlled methods forremoval of exposed material. Chemical etching is used for a variety ofpurposes including transferring a pattern in photoresist into underlyinglayer, thinning layers or thinning lateral dimensions of featuresalready present on the surface. Often it is desirable to have an etchprocess which etches one material faster than another helping e.g. apattern transfer process proceed. Such an etch process is said to beselective to the first material. As a result of the diversity ofmaterials, circuits and processes, etch processes have been developedwith a selectivity towards a variety of materials.

Dry etch processes are often desirable for selectively removing materialfrom semiconductor substrates. The desirability stems from the abilityto gently remove material from miniature structures with minimalphysical disturbance. Dry etch processes also allow the etch rate to beabruptly stopped by removing the gas phase reagents. Some dry-etchprocesses involve the exposure of a substrate to remote plasmaby-products formed from one or more precursors. For example, remoteplasma excitation of ammonia and nitrogen trifluoride enables siliconoxide to be selectively removed from a patterned substrate when theplasma effluents are flowed into the substrate processing region. Remoteplasma etch processes have recently been developed to selectively removea variety of dielectrics relative to one another. However, fewerdry-etch processes have been developed to evenly and selectively removemetals and/or their oxidation.

Methods are needed to evenly and selectively etch oxidation layers frommetal surfaces using dry etch processes.

BRIEF SUMMARY OF THE INVENTION

A method for conformal dry etch of a liner material in a high aspectration trench is achieved by depositing or forming an inhomogeneouspassivation layer which is thicker near the opening of a trench butthinner deep within the trench. The methods described herein use aselective etch following formation of the inhomogeneous passivationlayer. The selective etch etches liner material faster than thepassivation material. The inhomogeneous passivation layer suppresses theetch rate of the selective etch near the top of the trench (where itwould otherwise be fastest) and gives the etch a head start deeper inthe trench (where it would otherwise be slowest). This method may alsofind utility in removing bulk material uniformly from within a trench.

Embodiments of the invention include methods of etching material from ahigh aspect ratio trench on a patterned substrate. The methods includethe sequential steps of (1) providing a patterned substrate having aconformal liner layer on walls of the high aspect ratio trench, and (2)forming an inhomogeneous passivation layer over the conformal linerlayer in the high aspect ratio trench. The inhomogeneous passivationlayer has an outer passivation thickness near the opening of the highaspect ratio trench which is greater than an inner passivation thicknessdeep within the high aspect ratio trench. The sequential steps alsoinclude (3) gas phase etching the conformal liner layer. The gas phaseetching process selectively removes material from the conformal linerlayer faster than material from the inhomogeneous passivation layer. Thesequential steps further include (4) removing the remainder of theinhomogeneous passivation layer to leave a remainder of the conformalliner layer. The remainder of the conformal liner layer has an outerremaining conformal liner thickness near the opening of the high aspectratio trench and an inner remaining conformal liner thickness deepwithin the high aspect ratio trench. The outer remaining conformal linerthickness is greater than the inner remaining conformal liner thickness.The sequential steps further include (5) gas phase etching the remainderof the conformal liner layer to leave nearly vertical walls on the sidesof the high aspect ratio trench.

Additional embodiments and features are set forth in part in thedescription that follows, and in part will become apparent to thoseskilled in the art upon examination of the specification or may belearned by the practice of the disclosed embodiments. The features andadvantages of the disclosed embodiments may be realized and attained bymeans of the instrumentalities, combinations, and methods described inthe specification.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of the inventionmay be realized by reference to the remaining portions of thespecification and the drawings, presented below. The Figures areincorporated into the detailed description portion of the invention.

FIG. 1 is a cross-sectional schematic before and after a prior artetching of a liner material in a high aspect ratio trench.

FIG. 2 is a flowchart depicting steps of a method for conformal dry etchin a high aspect ratio trench according to embodiments of the invention.

FIG. 3 is a collection of cross-sectional schematics at several stagesduring the dry etch method of FIG. 2 according to embodiments of theinvention.

FIG. 4A shows a substrate processing chamber according to embodiments ofthe invention.

FIG. 4B shows a showerhead of a substrate processing chamber accordingto embodiments of the invention.

FIG. 5 shows a substrate processing system according to embodiments ofthe invention.

In the appended figures, similar components and/or features may have thesame reference label. Further, various components of the same type maybe distinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If only the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label.

DETAILED DESCRIPTION OF THE INVENTION

A method for conformal dry etch of a liner material in a high aspectratio trench is achieved by depositing or forming an inhomogeneouspassivation layer which is thicker near the opening of a trench butthinner deep within the trench. The methods described herein use aselective etch following formation of the inhomogeneous passivationlayer. The selective etch etches liner material faster than thepassivation material. The inhomogeneous passivation layer suppresses theetch rate of the selective etch near the top of the trench (where itwould otherwise be fastest) and gives the etch a head start deeper inthe trench (where it would otherwise be slowest). This method may alsofind utility in removing bulk material uniformly from within a trench.

During gas phase etch processes, etchant precursors have been found tolose some effectiveness progressively as they diffuse deeper within ahigh aspect ratio trench. This results from the increased number ofcollisions which occur as the aspect ratio is increased. Etchantprecursors have been found to lose some effectiveness progressively asthey diffuse deeper within a high aspect ratio trench. This results fromthe increased number of collisions which occur as the aspect ratio isincreased. FIG. 1 shows the result of a prior art process applied to atrench formed in a patterned substrate 100. The walls 105 of the trenchare lined with a conformal liner 110-1. Since the etch rate is faster atthe top of high aspect ratio trench than at the bottom, the post etchliner 110-2 displays a V shape instead of a uniform width from top tobottom as in the pre-etch condition.

This is an invention to achieve conformal etch in high aspect ratiostructure in semiconductor IC fabrication. The inventors have found anew method of uniform removal of material within a high aspect ratiotrench. In order to better understand and appreciate the invention,reference is now made to FIGS. 2-3 FIG. 2 is a flowchart of a conformaldry etch process sequence according to embodiments of the inventionwhile FIG. 3 is a collection of schematics at various points during theprocess sequence of FIG. 2. This invention achieves conformal dry etchin high aspect ratio trench. A patterned substrate with a high aspectratio trench is provided (operation 202). The high aspect ratio trenchis formed by walls 305 which are lined with conformal liner layer 310-1(which may or may not be the same material as the walls 305). Aninhomogeneous passivation layer 320-1 is then formed (operation 204) andis thicker near the top of the trench and relatively thin deeper withinthe trench as shown in the second panel of FIG. 3.

After passivation (204), a selective gas phase etch is applied(operation 206). Selective gas phase etch removes conformal liner 310-1material faster than inhomogeneous passivation layer 320-1 material. Asa consequence, the presence of inhomogeneous passivation layer 320-1increases the etch rate deep within the trench which counteracts the gasphase etches natural tendency to remove excess material at the top ofthe trench. The inhomogeneous passivation layer 320-1 is optionallyremoved in operation 208. In disclosed embodiments, the no inhomogeneouspassivation layer 320-1 material remains after selective gas phase etch(operation 206) and operation 208 becomes redundant. Operation 208 isnecessary especially if materials are selected such that the selectivegas phase etch is highly selective of the conformal liner 310-1 materialover inhomogeneous passivation layer 320-1 material.

A second gas phase etch step (operation 210) is applied to the remainingliner material 310-2. This time around, the natural tendency of the gasphase etch to etch more quickly near the opening of the trench iscompensated by the fact that there is more material to etch near theopening. In this way, the compound etch described and claimed herein canuniformly remove a conformal liner at an even etch rate. The overallresult is a conformal etch with similar etch amount across the depth ofthe trench.

In disclosed embodiments, the inhomogeneous passivation layer is formedby consuming some material from the conformal liner layer such that theconformal liner layer is thinner near the opening of the trench andthicker deep within the trench. In this embodiment, the conformal linerlayer is no longer conformal following the formation of theinhomogeneous passivation layer, however, the adjective “conformal” willstill be used in order to keep layer references straight.

The inner remaining conformal liner thickness may be measured within thebottom 20%, within the bottom 10%, or within the bottom 5% of the highaspect ratio trench in embodiments of the invention. Likewise, the innerpassivation thickness may be measured within the bottom 20%, within thebottom 10%, or within the bottom 5% of the high aspect ratio trench. Atthe other end of the trench, the outer remaining conformal linerthickness may be measured within the top 20%, within the top 10%, orwithin the top 5% of the high aspect ratio trench. Lastly, the outerpassivation thickness may be measured within the top 20%, within the top10%, or within the top 5% of the high aspect ratio trench in disclosedembodiments.

The inner remaining conformal liner thickness is less than or about 20%,less than or about 10%, or less than or about 5% of the outer remainingconformal liner thickness in embodiments of the invention. In somecases, the inner remaining conformal liner thickness may be close to orzero nanometers.

In embodiments, the invention described may be used for the vertical 3DNAND memories fabrication. For this semiconductor application, there arehigh aspect trenches in multiple-bilayer film stacks. Lateral andconformal etch of one material of the bilayer against the other isrequired. This etch process benefits the application most when it isconformal, i.e. has similar etch rate from top to bottom across the deepholes or trenches.

Generally speaking, the compensation algorithm described herein willalso work for bulk materials. In such cases, the term liner layer willstill be used herein, however, it will refer to the portion of the bulkmaterial which is removed by the conformal gas phase etch processsequence. In other words, the conformal liner layer may be an outerportion of a bulk material within walls of the high aspect ratio trenchin disclosed embodiments.

In one material system example, the material of the conformal linerlayer to be etched is silicon (e.g. single crystal silicon, polysiliconor amorphous silicon in the form of a liner). The inhomogeneouspassivation layer is silicon oxide or silicon nitride, formed by anoxygen plasma, a nitrogen plasma or a carbon plasma treatment of thesilicon liner. The source of oxygen, nitrogen or carbon (e.g. O₂, NH₃,or CH₄) may be delivered to a local plasma excitation within thesubstrate processing region to from the inhomogeneous passivation layerof silicon oxide, silicon nitride or silicon carbide. Hybridizedmaterials such as silicon oxynitride, silicon oxycarbide or siliconcarbon nitride may also be created to form the inhomogeneous passivationlayer. In these exemplary processes, some of the silicon in the siliconlayer is consumed.

In another material system example, the material of the conformal linerlayer to be etched is silicon oxide and the inhomogeneous passivationlayer is silicon or silicon nitride. In another material system example,the material to be etched is silicon nitride and the inhomogeneouspassivation layer is silicon or silicon oxide. In another example, thematerial to be etched in tungsten, and the passivation layer is tungstenoxide or tungsten nitride. The conformal liner layer may also betitanium and the inhomogeneous passivation layer is either titaniumoxide or titanium nitride in disclosed embodiments.

The aspect ratio of the high aspect ratio trenches may be greater than10:1 (height in width), greater than 25:1, greater than 30:1, greaterthan 50:1, greater than 75:1 or greater than 100:1 in embodiments of theinvention. As a result of the diversity of integrated circuit techniquesused today, the Applicants envision considerable latitude in theabsolute length scales which fall into these aspect ratio regmines. Inone example, conformal etch is achieved for a high aspect ratio trenchwith a width of 20 nm to 50 nm and a depth of 1μm to 2 μm. The conformaletch may be applied to a high aspect ratio trench having a depth greaterthan 0.5 μm, greater than 1.0 μm or greater than 2.0 μm in disclosedembodiments. The trench may have a width less than 50 nm, less than 30nm or less than 25 nm in embodiments of the invention.

Additional process parameters are disclosed in the course of describingan exemplary processing methods and systems.

Exemplary Processing Methods and Systems

Processing chambers that may implement embodiments of the presentinvention may be included within processing platforms such as theCENTURA® and PRODUCER® systems, available from Applied Materials, Inc.of Santa Clara, Calif. Examples of substrate processing chambers thatcan be used with exemplary methods of the invention may include thoseshown and described in co-assigned U.S. Provisional Patent App. No.60/803,499 to Lubomirsky et al, filed May 30, 2006, and titled “PROCESSCHAMBER FOR DIELECTRIC GAPFILL,” the entire contents of which is hereinincorporate by reference for all purposes. Additional exemplary systemsmay include those shown and described in U.S. Pat. Nos. 6,387,207 and6,830,624, which are also incorporated herein by reference for allpurposes. Selective etches with high selectivities available for a broadarray of materials find utility as the gas phase etch used herein.Chambers and processes with appropriate selectivities may be producedfrom Applied Materials, Santa Clara, Calif.

Generally speaking, selective etches have been created for a widevariety of inhomogeneous patterned substrates by flowing afluorine-containing precursor through a remote plasma system or a remoteplasma region in general (including the possibility of a chamber plasmaregion as described below). Supplementary precursors may be introducedto determine the selectivity. Supplementary precursors are either flowedthrough the remote plasma region or directly into the substrateprocessing system. The substrate temperature has also been found to be ahelpful parameter for determining the selectivity. In some cases theremote plasma power level, the process pressure and the precursor flowratios have also been used to obtain a desirable selectivity. Describingan exemplary processing chamber will help to convey the ways in whichthese process parameters are controlled.

FIG. 4A is a substrate processing chamber 1001 according to disclosedembodiments. A remote plasma system 1010 may process afluorine-containing precursor and/or a secondary precursor which thentravels through a gas inlet assembly 1011. Two distinct gas supplychannels are visible within the gas inlet assembly 1011. A first channel1012 carries a gas that passes through the remote plasma system 1010(RPS), while a second channel 1013 bypasses the remote plasma system1010. Either channel may be used for the fluorine-containing precursor,in embodiments. On the other hand, the first channel 1012 may be usedfor the process gas and the second channel 1013 may be used for atreatment gas. The lid (or conductive top portion) 1021 and a perforatedpartition 1053 are shown with an insulating ring 1024 in between, whichallows an AC potential to be applied to the lid 1021 relative toperforated partition 1053. The AC potential strikes a plasma in chamberplasma region 1020. The process gas may travel through first channel1012 into chamber plasma region 1020 and may be excited by a plasma inchamber plasma region 1020 alone or in combination with remote plasmasystem 1010. If the process gas (the fluorine-containing precursor)flows through second channel 1013, then only the chamber plasma region1020 is used for excitation. The combination of chamber plasma region1020 and/or remote plasma system 1010 may be referred to as a remoteplasma system herein. The perforated partition (also referred to as ashowerhead) 1053 separates chamber plasma region 1020 from a substrateprocessing region 1070 beneath showerhead 1053. Showerhead 1053 allows aplasma present in chamber plasma region 1020 to avoid directly excitinggases in substrate processing region 1070, while still allowing excitedspecies to travel from chamber plasma region 1020 into substrateprocessing region 1070.

Showerhead 1053 is positioned between chamber plasma region 1020 andsubstrate processing region 1070 and allows plasma effluents (excitedderivatives of precursors or other gases) created within remote plasmasystem 1010 and/or chamber plasma region 1020 to pass through aplurality of through-holes 1056 that traverse the thickness of theplate. The showerhead 1053 also has one or more hollow volumes 1051which can be filled with a precursor in the form of a vapor or gas (suchas a silicon-containing precursor) and pass through small holes 1055into substrate processing region 1070 but not directly into chamberplasma region 1020. Showerhead 1053 is thicker than the length of thesmallest diameter 1050 of the through-holes 1056 in this disclosedembodiment. In order to maintain a significant concentration of excitedspecies penetrating from chamber plasma region 1020 to substrateprocessing region 1070, the length 1026 of the smallest diameter 1050 ofthe through-holes may be restricted by forming larger diameter portionsof through-holes 1056 part way through the showerhead 1053. The lengthof the smallest diameter 1050 of the through-holes 1056 may be the sameorder of magnitude as the smallest diameter of the through-holes 1056 orless in disclosed embodiments.

Showerhead 1053 may be configured to serve the purpose of an ionsuppressor as shown in FIG. 4A. Alternatively, a separate processingchamber element may be included (not shown) which suppresses the ionconcentration traveling into substrate processing region 1070. Lid 1021and showerhead 1053 may function as a first electrode and secondelectrode, respectively, so that lid 1021 and showerhead 1053 mayreceive different electric voltages. In these configurations, electricalpower (e.g., RF power) may be applied to lid 1021, showerhead 1053, orboth. For example, electrical power may be applied to lid 1021 whileshowerhead 1053 (serving as ion suppressor) is grounded. The substrateprocessing system may include a RF generator that provides electricalpower to the lid and/or showerhead 1053. The voltage applied to lid 1021may facilitate a uniform distribution of plasma (i.e., reduce localizedplasma) within chamber plasma region 1020. To enable the formation of aplasma in chamber plasma region 1020, insulating ring 1024 mayelectrically insulate lid 1021 from showerhead 1053. Insulating ring1024 may be made from a ceramic and may have a high breakdown voltage toavoid sparking. Portions of substrate processing chamber 1001 near thecapacitively-coupled plasma components just described may furtherinclude a cooling unit (not shown) that includes one or more coolingfluid channels to cool surface exposed to the plasma with a circulatingcoolant (e.g., water).

In the embodiments shown, showerhead 1053 may distribute (viathrough-holes 1056) process gases which contain fluorine, hydrogenand/or plasma effluents of such process gases upon excitation by aplasma in chamber plasma region 1020. In embodiments, the process gasintroduced into the remote plasma system 1010 and/or chamber plasmaregion 1020 may contain fluorine (e.g. F₂, NF₃ or XeF₂). The process gasmay also include a carrier gas such as helium, argon, nitrogen (N₂),etc. Plasma effluents may include ionized or neutral derivatives of theprocess gas and may also be referred to herein as radical-fluorineand/or radical-hydrogen referring to the atomic constituent of theprocess gas introduced.

Through-holes 1056 are configured to suppress the migration ofionically-charged species out of the chamber plasma region 1020 whileallowing uncharged neutral or radical species to pass through showerhead1053 into substrate processing region 1070. These uncharged species mayinclude highly reactive species that are transported with less-reactivecarrier gas by through-holes 1056. As noted above, the migration ofionic species by through-holes 1056 may be reduced, and in someinstances completely suppressed. Controlling the amount of ionic speciespassing through showerhead 1053 provides increased control over the gasmixture brought into contact with the underlying wafer substrate, whichin turn increases control of the deposition and/or etch characteristicsof the gas mixture. For example, adjustments in the ion concentration ofthe gas mixture can alter the etch selectivity (e.g., the tungstenoxide:tungsten etch ratio).

In embodiments, the number of through-holes 1056 may be between about 60and about 2000. Through-holes 1056 may have a variety of shapes but aremost easily made round. The smallest diameter 1050 of through-holes 1056may be between about 0.5 mm and about 20 mm or between about 1 mm andabout 6 mm in disclosed embodiments. There is also latitude in choosingthe cross-sectional shape of through-holes, which may be made conical,cylindrical or combinations of the two shapes. The number of small holes1055 used to introduce unexcited precursors into substrate processingregion 1070 may be between about 100 and about 5000 or between about 500and about 2000 in different embodiments. The diameter of the small holes1055 may be between about 0.1 mm and about 2 mm.

Through-holes 1056 may be configured to control the passage of theplasma-activated gas (i.e., the ionic, radical, and/or neutral species)through showerhead 1053. For example, the aspect ratio of the holes(i.e., the hole diameter to length) and/or the geometry of the holes maybe controlled so that the flow of ionically-charged species in theactivated gas passing through showerhead 1053 is reduced. Through-holes1056 in showerhead 1053 may include a tapered portion that faces chamberplasma region 1020, and a cylindrical portion that faces substrateprocessing region 1070. The cylindrical portion may be proportioned anddimensioned to control the flow of ionic species passing into substrateprocessing region 1070. An adjustable electrical bias may also beapplied to showerhead 1053 as an additional means to control the flow ofionic species through showerhead 1053.

Alternatively, through-holes 1056 may have a smaller inner diameter (ID)towards the top surface of showerhead 1053 and a larger ID toward thebottom surface. In addition, the bottom edge of through-holes 1056 maybe chamfered to help evenly distribute the plasma effluents in substrateprocessing region 1070 as the plasma effluents exit the showerhead andthereby promote even distribution of the plasma effluents and precursorgases. The smaller ID may be placed at a variety of locations alongthrough-holes 1056 and still allow showerhead 1053 to reduce the iondensity within substrate processing region 1070. The reduction in iondensity results from an increase in the number of collisions with wallsprior to entry into substrate processing region 1070. Each collisionincreases the probability that an ion is neutralized by the acquisitionor loss of an electron from the wall. Generaly speaking, the smaller IDof through-holes 1056 may be between about 0.2 mm and about 20 mm. Inother embodiments, the smaller ID may be between about 1 mm and 6 mm orbetween about 0.2 mm and about 5 mm. Further, aspect ratios of thethrough-holes 1056 (i.e., the smaller ID to hole length) may beapproximately 1 to 20. The smaller ID of the through-holes may be theminimum ID found along the length of the through-holes. The crosssectional shape of through-holes 1056 may be generally cylindrical,conical, or any combination thereof.

FIG. 4B is a bottom view of a showerhead 1053 for use with a processingchamber according to disclosed embodiments. Showerhead 1053 correspondswith the showerhead shown in FIG. 4A. Through-holes 1056 are depictedwith a lager-diameter (ID) on the bottom of showerhead 1053 and asmaller ID at the top. Small holes 1055 are distributed substantiallyevenly over the surface of the showerhead, even amongst thethrough-holes 1056 which helps to provide more even mixing than otherembodiments described herein.

An exemplary patterned substrate may be supported by a pedestal (notshown) within substrate processing region 1070 when fluorine-containingplasma effluents and oxygen-containing plasma effluents arrive throughthrough-holes 1056 in showerhead 1053. Though substrate processingregion 1070 may be equipped to support a plasma for other processes suchas curing, no plasma is present during the etching of patternedsubstrate, in embodiments of the invention.

A plasma may be ignited either in chamber plasma region 1020 aboveshowerhead 1053 or substrate processing region 1070 below showerhead1053. A plasma is present in chamber plasma region 1020 to produce theradical-fluorine from an inflow of the fluorine-containing precursor. AnAC voltage typically in the radio frequency (RF) range is appliedbetween the conductive top portion (lid 1021) of the processing chamberand showerhead 1053 to ignite a plasma in chamber plasma region 1020during deposition. An RF power supply generates a high RF frequency of13.56 MHz but may also generate other frequencies alone or incombination with the 13.56 MHz frequency.

The top plasma may be left at low or no power when the bottom plasma inthe substrate processing region 1070 is turned on to either cure a filmor clean the interior surfaces bordering substrate processing region1070. A plasma in substrate processing region 1070 is ignited byapplying an AC voltage between showerhead 1053 and the pedestal orbottom of the chamber. A cleaning gas may be introduced into substrateprocessing region 1070 while the plasma is present.

The pedestal may have a heat exchange channel through which a heatexchange fluid flows to control the temperature of the substrate. Thisconfiguration allows the substrate temperature to be cooled or heated tomaintain relatively low temperatures (from room temperature throughabout 120° C.). The heat exchange fluid may comprise ethylene glycol andwater. The wafer support platter of the pedestal (preferably aluminium,ceramic, or a combination thereof) may also be resistively heated inorder to achieve relatively high temperatures (from about 120° C.through about 1100° C.) using an embedded single-loop embedded heaterelement configured to make tow full turns in the form of parallelconcentric circles. An outer portion of the heater element may runadjacent to a perimeter of the support platter, while an inner portionruns on the path of a concentric circle having a smaller radius. Thewiring to the heater element passes through the stem of the pedestal.

The chamber plasma region or a region in a remote plasma system may bereferred to as a remote plasma region. In embodiments, the radicalprecursors (e.g. radical-fluorine and any secondary radical precursors)are formed in the remote plasma region and travel into the substrateprocessing region where the combinations preferentially etches, forexample, polysilicon, silicon oxide, silicon nitride, titanium nitrideand tungsten oxide. Plasma power may essentially be applied only to theremote plasma region, in embodiments, to ensure that theradical-fluorine and any secondary radical precursors (which togethermay be referred to as plasma effluents) are not further excited in thesubstrate processing region. Addition of an unexcited precursor (e.g.water, an alcohol or amine-containing precursor) has also provendesirable as an alternative to a secondary radical precursor in order toextend the range of gas-phase etches in selectivity-space.

In embodiments employing a chamber plasma region, the excited plasmaeffluents are generated in a section of the substrate processing regionpartitioned from a deposition region. The deposition region, also knownherein as the substrate processing region, is where the plasma effluentsmix and react to etch the patterned substrate (e.g., a semiconductorwafer). The excited plasma effluents may also be accompanied by inertgases (in the exemplary case, argon). The substrate processing regionmay be described herein as “plasma-free” during etching of thesubstrate. “Plasma-free” does not necessarily mean the region is devoidof plasma. A relatively low concentration of ionized species and freeelectrons created within the plasma region do travel through pores(apertures) in the partition (showerhead/ion suppressor) due to theshapes and sizes of through-holes 1056. In some embodiments, there isessentially no concentration of ionized species and free electronswithin the substrate processing region. The borders of the plasma in thechamber plasma region are hard to define and may encroach upon thesubstrate processing region through the apertures in the showerhead. Inthe case of an inductively-coupled plasma, a small amount of ionizationmay be effected within the substrate processing region directly.Furthermore, a low intensity plasma may be created in the substrateprocessing region without eliminating desirable features of the formingfilm. All causes for a plasma having much lower intensity ion densitythan the chamber plasma region (or a remote plasma region, for thatmatter) during the creation of the excited plasma effluents do notdeviate from the scope of “plasma-free” as used herein.

Nitrogen trifluoride (or another fluorine-containing precursor) may beflowed into chamber plasma region 1020 at rates between about 5 sccm andabout 500 sccm, between about 10 sccm and about 300 sccm, between about25 sccm and about 200 sccm, between about 50 sccm and about 150 sccm orbetween about 75 sccm and about 125 sccm in disclosed embodiments.Combined flow rates of fluorine-containing precursor and secondaryprecursors into the chamber may account for 0.05% to about 20% by volumeof the overall gas mixture; the remainder being carrier gases. In thecase of the fluorine-containing precursor, a purge or carrier gas may befirst initiated into the remote plasma region before those of thefluorine-containing gas to stabilize the pressure within the remoteplasma region.

Plasma power applied to the remote plasma region can be a variety offrequencies or a combination of multiple frequencies. In the exemplaryprocessing system the plasma is provided by RF power delivered betweenlid 1021 and showerhead 1053. In an embodiment, the energy is appliedusing a capacitively-coupled plasma unit. When using a Frontier™ orsimilar system, the remote plasma source power may be between about 300watts and about 2000 watts, or between about 500 watts and about 1500watts in embodiments of the invention. The RF frequency applied in theexemplary processing system may be a low RF frequencies less than about200 kHz, high RF frequencies between about 10 MHz and about 15 MHz ormicrowave frequencies greater than or about 1 GHz in differentembodiments.

Substrate processing region 1070 can be maintained at a variety ofpressures during the flow of carrier gases and plasma effluents intosubstrate processing region 1070. The pressure within the substrateprocessing region is below or about 50 Torr, below or about 30 Torr,below or about 20 Torr, below or about 10 Torr or below or about 5 Torr.The pressure may be above or about 0.1 Torr, above or about 0.2 Torr,above or about 0.5 Torr or above or about 1 Torr in embodiments of theinvention. Lower limits on the pressure may be combined with upperlimits on the pressure to arrive at further embodiments of theinvention.

In one or more embodiments, the substrate processing chamber 1001 can beintegrated into a variety of multi-processing platforms, including theProducer™ GT, Centura™ AP and Endura™ platforms available from AppliedMaterials, Inc. located in Santa Clara, Calif. Such a processingplatform is capable of performing several processing operations withoutbreaking vacuum. Processing chambers that may implement embodiments ofthe present invention may include dielectric etch chambers or a varietyof chemical vapor deposition chambers, among other types of chambers.

Embodiments of the deposition systems may be incorporated into largerfabrication systems for producing integrated circuit chips. FIG. 5 showsone such system 1101 of deposition, baking and curing chambers accordingto disclosed embodiments. In the figure, a pair of FOUPs (front openingunified pods) 1102 supply substrate substrates (e.g., 300 mm diameterwafers) that are received by robotic arms 1104 and placed into a lowpressure holding areas 1106 before being placed into one of the waferprocessing chambers 1108 a-f. A second robotic arm 1110 may be used totransport the substrate wafers from the low pressure holding areas 1106to the wafer processing chambers 1108 a-f and back. Each waferprocessing chamber 1108 a-f, can be outfitted to perform a number ofsubstrate processing operations including the dry etch processesdescribed herein in addition to cyclical layer deposition (CLD), atomiclayer deposition (ALD), chemical vapor deposition (CVD), physical vapordeposition (PVD), etch, pre-clean, degas, orientation and othersubstrate processes.

The wafer processing chamber 1108 a-f may include one or more systemcomponents for depositing, annealing, curing and/or etching a flowabledielectric film on the substrate wafer. In one configuration, two pairsof the processing chamber (e.g., 1108 c-d and 1108 e-f) may be used todeposit dielectric material on the substrate, and the third pair ofprocessing chambers (e.g., 1108 a-b) may be used to etch the depositeddielectric. In another configuration, all three pair of chambers (e.g.,1108 a-f) may be configured to etch a dielectric film on the substrate.Any one or ore of the processes described may be carried out onchamber(s) separated from the fabrication system shown in differentembodiments.

The substrate processing system is controlled by a system controller. Inan exemplary embodiment, the system controller includes a hard diskdrive, a floppy disk drive and a processor. The processor contains asingle-board computer (SBC), analog and digital input/output boards,interface boards and stepper motor controller boards. Various parts ofCVD system conform to the Versa Modular European (VME) standard whichdefines board, card cage, and connector dimensions and types. The VMEstandard also defines the bus structure as having a 16-bit data bus anda 24-bit address bus.

System controller 1157 is used to control motors, valves, flowcontrollers, power supplies and other functions required to carry outprocess recipes described herein. A gas handling system 1155 may also becontrolled by system controller 1157 to introduce gases to one or all ofthe wafer processing chambers 1108 a-f. System controller 1157 may relyon feedback from optical sensors to determine and adjust the position ofmovable mechanical assemblies in gas handling system 1155 and/or inwafer processing chambers 1108 a-f. Mechanical assemblies may includethe robot, throttle valves and susceptors which are moved by motorsunder the control of system controller 1157.

In an exemplary embodiment, system controller 1157 includes a hard diskdrive (memory), USB ports, a floppy disk drive and a processor. Systemcontroller 1157 includes analog and digital input/output boards,interface boards and stepper motor controller boards. Various parts ofmulti-chamber processing system 1101 which contains substrate processingchamber 1001 are controlled by system controller 1157. The systemcontroller executes system control software in the form of a computerprogram stored on computer-readable medium such as a hard disk, a floppydisk or a flash memory thumb drive. Other types of memory can also beused. The computer program includes sets of instructions that dictatethe timing, mixture of gases, chamber pressure, chamber temperature, RFpower levels, susceptor position, and other parameters of a particularprocess.

A process for etching, depositing or otherwise processing a film on asubstrate or a process for cleaning chamber can be implemented using acomputer program product that is executed by the controller. Thecomputer program code can be written in any conventional computerreadable programming language: for example, 68000 assembly language, C,C++, Pascal, Fortran or others. Suitable program code is entered into asingle file, or multiple files, using a conventional text editor, andstored or embodied in a computer usable medium, such as a memory systemof the computer. If the entered code text is in a high level language,the code is complied, and the resultant compiler code is then linkedwith an object code of precomplied Microsoft Windows™ library routines.To execute the linked, complied object code the system user invokes theobject code, causing the computer system to load the code in memory. TheCPU then reads and executes the code to perform the tasks indentified inthe program.

The interface between a user and the controller may be via atouch-sensitive monitor and may also include a mouse and keyboard. Inone embodiment two monitors are used, one mounted in the clean room wallfor the operators and the other behind the wall for the servicetechnicians. The two monitors may simultaneously display the sameinformation, in which case only one is configured to accept input at atime. To select a particular screen or function, the operator touches adesignated area on the display screen with a finger or the mouse. Thetouched area changes its highlighted color, or a new menu or screen isdisplayed, confirming the operator's selection.

As used herein “substrate” may be a support substrate with or withoutlayers formed thereon. The patterned substrate may be an insulator or asemiconductor of a variety of doping concentrations and profiles andmay, for example, be a semiconductor substrate of the type used in themanufacture of integrated circuits. Exposed “silicon” of the patternedsubstrate is predominantly Si but may include minority concentrations ofother elemental constituents such as nitrogen, oxygen, hydrogen, carbonand the like. Exposed “silicon nitride” of the patterned substrate ispredominantly Si₃N₄ but may include minority concentrations of otherelemental constituents such as oxygen, hydrogen, carbon and the like.Exposed “silicon oxide” of the patterned substrate is predominantly SiO₂but may include minority concentrations of other elemental constituentssuch as nitrogen, hydrogen, carbon and the like. In some embodiments,silicon oxide films etched using the methods disclosed herein consistessentially of silicon and oxygen. “Tungsten oxide” is predominantlytungsten and oxygen but may include minority concentrations of otherelemental constituents such as nitrogen, hydrogen, carbon and the like.Tungsten oxide may consist of tungsten and oxygen. “Titanium nitride” ispredominantly titanium and nitrogen but may include minorityconcentrations of other elemental constituents such as nitrogen,hydrogen, carbon and the like. Titanium nitride may consist of titaniumand nitrogen.

The term “precursor” is used to refer to any process gas which takespart in a reaction to either remove material from or deposit materialonto a surface. “Plasma effluents” describe gas exiting from the chamberplasma region and entering the substrate processing region. Plasmaeffluents are in an “excided state” wherein at least some of the gasmolecules are in vibrationally-excited, dissociated and/or ionizedstates. A “radical precursor” is used to describe plasma effluents (agas in an excited state which is exiting a plasma) which participate ina reaction to either remove material from or deposit material on asurface. “Radical-fluorine” (or “radical-hydrogen” or “radical-oxygen”)are radical precursors which contain fluorine (or hydrogen) but maycontain other elemental constituents. The phrase “inert gas” refers toany gas which does not form chemical bonds when etching or beingincorporated into a film. Exemplary inert gases include noble gases butmay include other gases so long as no chemical bonds are formed when(typically) trace amounts are trapped in a film.

The phrase “high aspect ratio” may refer to structures like deep gaps orholes. Regardless of shape as viewed from above, all high speed ratiostructures will be referred to as “trenches” herein. The term “gap” and“trench” are used throughout with no implication that the etchedgeometry has a large horizontal aspect ratio. Viewed from above thesurface, trenches may appear circular, oval, polygonal, rectangular, ora variety of other shapes. A trench may be in the shape of a moat aroundan island of material. The term “via” is used to refer to a low aspectratio trench (as viewed from above) which may or may not be filled withmetal to form a vertical electrical connection. As used herein, aconformal etch process refers to a generally uniform removal of materialon a surface in the same shape as the surface, i.e., the surface of theetched layer and the pre-etch surface are generally parallel. A personhaving ordinary skill in the art will recognize that the etchedinterface likely cannot be 100% conformal and thus the term “generally”allows for acceptable tolerances.

Having disclosed several embodiments, it will be recognized by thoseskilled in the art that various modifications, alternativeconstructions, and equivalents may be used without departing from thespirit of the disclosed embodiments. Additionally, a number of wellknown processes and elements have not been described in order to avoidunnecessarily obscuring the present invention. Accordingly, the abovedescription should not be taken as limiting the scope of the invention.

Where a range of values is provided, it is understood that eachintervening value, to the tenth of the unit of the lower limit unlessthe context clearly dictates otherwise, between the upper and lowerlimits of that range is also specifically disclosed. Each smaller rangebetween any states value or intervening value in a stated range and anyother stated or intervening value in that stated range is encompassed.The upper and lower limits of these smaller ranges may independently beincluded or excluded in the range, and each range where wither, neitheror both limits are included in the smaller ranges is also encompassedwithin the invention, subject to any specifically excluded limit in thestated range. Where the stated range includes one or both of the limits,ranges excluding either or both of those included limits are alsoincluded.

As used herein and in the appended claims, the singular forms “a”, “an”,and “the” include plural referents unless the context clearly dictatesotherwise. Thus, for example, reference to “a process” includes aplurality of such processes and references to “the dielectric material”includes reference to one or more dielectric materials and equivalentsthereof known to those skilled in the art, and so forth.

Also, the words “comprise,” “comprising,” “include,” “including,” and“includes” when used in this specification and in the following claimsare intended to specify the presence of stated features, integers,components, or steps, but they do not preclude the presence or additionof one or more other features, integers, components, steps, acts, orgroups.

What is claimed is:
 1. A method of etching material from a high aspectratio trench on a patterned substrate, the method comprising thesequential steps of: providing a patterned substrate having a conformalliner layer on walls of the high aspect ratio trench; forming aninhomogeneous passivation layer over the conformal liner layer in thehigh aspect ratio trench, wherein the inhomogeneous passivation layerhas an outer passivation thickness near the opening of the high aspectratio trench and an inner passivation thickness deep within the highaspect ratio trench, and wherein the outer passivation thickness isgreater than the inner passivation thickness; gas phase etching theconformal liner layer, wherein the gas phase etching process selectivelyremoves material from the conformal liner layer faster than materialfrom the inhomogeneous passivation layer; removing the remainder of theinhomogeneous passivation layer to leave a remainder of the conformalliner layer, wherein the remainder of the conformal liner layer has anouter remaining conformal liner thickness near the opening of the highaspect ratio trench and an inner remaining conformal liner thicknessdeep within the high aspect ratio trench, and wherein the outerremaining conformal liner thickness is greater than the inner remainingconformal liner thickness; gas phase etching the remainder of theconformal liner layer to leave nearly vertical walls on the sides of thehigh aspect ratio trench.
 2. The method of claim 1 wherein an aspectratio of the high aspect ratio trench may be greater than 10:1.
 3. Themethod of claim 1 wherein the inner passivation thickness is less thanor about 20% of the outer passivation thickness.
 4. The method of claim1 wherein the inner remaining conformal liner thickness is less than orabout 20% of the outer remaining conformal liner thickness.
 5. Themethod of claim 1 wherein the inner remaining conformal liner thicknessis measured within the bottom 20% of the high aspect ratio trench. 6.The method of claim 1 wherein the inner passivation thickness ismeasured within the bottom 20% of the high aspect ratio trench.
 7. Themethod of claim 1 wherein the outer remaining conformal liner thicknessis measured within the top 20% of the high aspect ratio trench.
 8. Themethod of claim 1 wherein the outer passivation thickness is measuredwithin the top 20% of the high aspect ratio trench.
 9. The method ofclaim 1 wherein the inhomogeneous passivation layer is formed byconsuming some material from the conformal liner layer such that theconformal liner layer is thinner near the opening of the trench andthicker deep within the trench.
 10. The method of claim 1 wherein theconformal liner layer is single crystal silicon, polysilicon oramorphous silicon.
 11. The method of claim 1 wherein the inhomogeneouspassivation layer is silicon oxide, silicon nitride, silicon oxynitride,silicon carbide, silicon oxycarbide or silicon carbon nitride.
 12. Themethod of claim 1 wherein the conformal liner layer is silicon oxide andthe inhomogeneous passivation layer is silicon nitride or silicon. 13.The method of claim 1 wherein the conformal liner layer is siliconnitride and the inhomogeneous passivation layer is silicon oxide orsilicon.
 14. The method of claim 1 wherein the conformal liner layer istungsten and the inhomogeneous passivation layer is tungsten oxide ortungsten nitride.
 15. The method of claim 1 wherein the conformal linerlayer is titanium and the inhomogeneous passivation layer is titaniumoxide or titanium nitride.
 16. The method of claim 1 wherein theconformal liner layer is an outer portion of a bulk material withinwalls of the high aspect ratio trench.
 17. The method of claim 1 whereinthe high aspect ratio trench has a depth greater than 0.5 μm.